Basis for original (SCP) IDLH: From the standpoint of deriving an appropriate IDLH, the soluble Ba compounds BaCl2 and Ba(NO3)2 prove to be the most acutely toxic. Browning [1969] reported that:

the toxic dose of BaCl2 for man was 200 to 500 mg [Lydtin et al. 1965]; Patty [1963] cited 800 to 900 mg of BaCl2 (550 to 600 mg as Ba) as the fatal dose for man [Sollman 1953]. Acute toxicity data in animals show Ba(NO3)2 equally as toxic as BaCl2. As no data on the acute inhalation toxicity of either of these two barium compounds exist, the IDLH is based on a calculated dose for a 30-minute exposure for man required to attain an intake of 200 mg BaCl2 (as Ba), assuming a minute volume of 7.5 liters/minute and an 80% retention. Therefore, the IDLH is calculated to be about 1,100 mg Ba/m3. However, respirators have been selected on the basis of the assigned protection factor afforded by each device up to 500 x the OSHA PEL of 0.5 mg Ba/m3 (i.e., 250 mg Ba/m3); only the “most protective” respirators are permitted for use in concentrations exceeding 250 mg Ba/m3. Short-term exposure guidelines . None developed

ACUTE TOXICITY DATA

Lethal dose data:

Species

Reference

Route

LD50

LDLo

Adjusted LD

Derived Value

BaCl2

Rabbit

Barnes and Eltherington 1973

oral

—–

112 mg Ba/kg

785 mg Ba/m3

79 mg Ba/m3

Dog

Barnes and Eltherington 1973

oral

—–

59 mg Ba/kg

16 mg Ba/m3

42 mg Ba/m3

Rat

Calvery 1942

oral

78 mg

—–

545 mg Ba/m3

55 mg Ba/m3

G. pig

Calvery 1942

oral

50 mg

—–

350 mg Ba/m3

35 mg Ba/m3

Mouse

Coulston and Korte 1975

oral

—–

46 mg Ba/kg

323 mg Ba/m3

32 mg Ba/m3

Ba(NO3)2

Rat

Marhold 1972

oral

187 mg

—–

1,306 mg Ba/m3

131 mg Ba/m3

Rabbit

Yakkyoku 1980

oral

—–

79 mg Ba/kg

552 mg Ba/m3

55 mg Ba/m3

Dog

Yakkyoku 1980

oral

—–

421 mg Ba/kg

2,944 mg Ba/m3

294 mg Ba/m3

Human data: It has been reported that the lethal oral dose is 43 to 57 mg Ba/kg Reeve 1979]. [Note: An oral dose of 43 to 57 mg Ba/kg is equivalent to a 70-kg worker being exposed to 2,007 to 2,660 mg/m3 for 30 minutes, assuming a breathing rate of 50 liters per minute and 100% absorption.]

Revised IDLH: 50 mg Ba/m3Basis for revised IDLH: Basis for “Revised” IDLH: No inhalation toxicity data are available on which to base an IDLH for soluble barium compounds. Therefore, the revised IDLH for soluble barium compounds is 50 mg Ba/m3 based on acute oral toxicity data in humans [Reeve 1979] and animals [Barnes and Eltherington 1973; Calvery 1942; Coulston and Korte 1975; Yakkyoku 1980]. This may be a conservative value due to the lack of relevant acute toxicity data for workers exposed to concentrations above 50 mg/m3.